During childbirth, medical personnel commonly monitor the degree of dilation of the mother's cervix, the location of the fetus within the cervix and uterus and the strength and frequency of the mother's labor contractions. Much of this monitoring is conducted by direct visual observation and manual palpation. Various instruments have been proposed to aid the monitoring process. As disclosed in the U.S. Pat. No. 5,438,996, a cervimeter for monitoring the degree of cervical dilation may be based on direct mechanical measurements; or on ultrasonic measurement. In the ultrasonic cervimeter, a small ultrasonic transmitting device is attached to the mother's cervix adjacent its opening, and a small receiving device is also attached to the cervix, but on the opposite of the opening. The time of flight of ultrasonic signals between the transmitter and receiver provides an indication of the distance between them and hence an indication of the degree of cervical dilation. As disclosed in the '996 patent, and as further described in U.S. Pat. No. 3,768,459, an electromagnetic cervimeter uses an electromagnetic transmitting coil attached to one side of the cervix and an electromagnetic receiving coil attached to the opposite side. The strength of electromagnetic coupling between these coils provides an indication of the distance between the transmitter and receiver and hence an indication of cervical dilation.
As described in U.S. Pat. No. 3,913,563, the magnitude of uterine contractions can be monitored by use of a strain gauge. A flexible reed is mounted on a frame carried by the belt. The belt holds the frame against the abdominal wall. The reed extends through the frame and also contacts the abdominal wall. Contractions cause movement of the reed. The degree of movement provides an indication of the magnitude of the muscle contraction. As described in U.S. Pat. Nos. 5,634,476 and 5,218,972, pressure measuring devices bearing on the abdomen can also be used to measure changes in pressure caused by the contractions.
Other monitoring devices used in childbirth are directed to monitoring the status of the fetus during these processes. For example, a pulse monitoring device may be physically mounted on the fetus, as by mounting the pulse monitoring device to the scalp of the fetus through the cervical opening.
Despite these efforts in the art, additional improvements in monitoring the childbirth process, and in monitoring the analogous process in non-human mammalian birth would be desirable.